fix: charts with multiple measures/dimensions drill down to Pivot, not TDD

- Block TDD when y.fields has multiple measures (multi-metric charts)
- Block TDD when both x is nominal and color is a dimension (multiple dims)
- Skip synthetic type:"value" fields (e.g. rill_measures color encoding) in
  transformChartSpecToPivotState so they don't appear as fake dimensions
- Place all non-measure fields in rows initially; when rows contain dimension
  chips, move time chips from rows to columns

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: TheRillJon

web-common/src/features/canvas/components/charts/util.ts

@@ -28,36 +28,41 @@ export function getLinkStateForTimeDimensionDetail(
   dimensionName?: string;
 } {
   if (!allowedTimeDimensionDetailTypes.includes(type))
-    return {
-      canLink: false,
-    };
+    return { canLink: false };
 
   const hasXAxis = "x" in spec;
   const hasYAxis = "y" in spec;
   if (!hasXAxis || !hasYAxis)
-    return {
-      canLink: false,
-    };
+    return { canLink: false };
 
   const xAxis = spec.x;
   const yAxis = spec.y;
 
-  if (isFieldConfig(xAxis) && isFieldConfig(yAxis)) {
-    const colorDimension = spec.color;
-    if (isFieldConfig(colorDimension)) {
-      return {
-        canLink: xAxis.type === "temporal",
-        measureName: yAxis.field,
-        dimensionName: colorDimension.field,
-      };
-    }
+  if (!isFieldConfig(xAxis) || !isFieldConfig(yAxis))
+    return { canLink: false };
 
+  if (yAxis.fields && yAxis.fields.length > 1)
+    return { canLink: false };
+
+  const colorDimension = spec.color;
+  const hasDimensionBreakout =
+    isFieldConfig(colorDimension) &&
+    colorDimension.type !== "quantitative" &&
+    colorDimension.type !== "value";
+
+  if (hasDimensionBreakout && xAxis.type === "nominal")
+    return { canLink: false };
+
+  if (hasDimensionBreakout) {
     return {
       canLink: xAxis.type === "temporal",
       measureName: yAxis.field,
+      dimensionName: colorDimension.field,
     };
   }
+
   return {
-    canLink: false,
+    canLink: xAxis.type === "temporal",
+    measureName: yAxis.field,
   };
 }

web-common/src/features/components/charts/explore-transformer.ts

@@ -33,6 +33,10 @@ export function transformChartSpecToPivotState(
 
     const fieldConfig = value;
 
+    if (fieldConfig.type === "value") {
+      continue;
+    }
+
     // Handle multiple fields case
     if (fieldConfig.fields?.length) {
       columns.push(
@@ -55,13 +59,24 @@ export function transformChartSpecToPivotState(
       type: chipType,
     };
 
-    if (key === "x" || chipType === PivotChipType.Measure) {
+    if (chipType === PivotChipType.Measure) {
       columns.push(chipData);
     } else {
       rows.push(chipData);
     }
   }
 
+  const hasDimensionRows = rows.some(
+    (r) => r.type === PivotChipType.Dimension,
+  );
+  if (hasDimensionRows) {
+    const timeChips = rows.filter((r) => r.type === PivotChipType.Time);
+    const nonTimeRows = rows.filter((r) => r.type !== PivotChipType.Time);
+    columns.push(...timeChips);
+    rows.length = 0;
+    rows.push(...nonTimeRows);
+  }
+
   return {
     columns,
     rows,